This application claims the priority of German patent 198 09 519.8, filed Mar. 5, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method and a device for removing a slug from a hydroforming tool.
A method and a device for removing a slug from a hydroforming tool are known from U.S. Pat. No. 5,398,533. The device in that patent incorporates a hydroforming tool that is divided along the length of the hollow profile inserted into the die. A recess is provided in the flat bottom surface of the die, which is trapezoidal in cross section. A die button is inserted into the recess for punching the hollow profile under internal high pressure. The die button is flush with the flat surface of the die and has an axial bore in which a plunger is guided. The bore has an annular cutting edge at its opening into the die. The plunger seals off the opening of the bore during the shaping of the hollow profile. Once the shaping process is complete, the plunger is retracted relatively abruptly. Then, under the influence of the internal high pressure that still prevails and because of the lack of support of the hollow profile by the plunger, the hollow profile is pressed against the cutting edge of the bore. Then a slug is separated from the hollow profile and pressed into the slug channel formed by the bore. The fluid pressure is then released and the plunger is lowered again until the slug resting on the end face of the plunger is level with a transverse channel leading to the slug channel that extends into the vicinity of the hydroforming tool. Then the removal tool, designed as a pusher, kicks the slug out of the slug channel through the transverse channel. The plunger is also mechanically driven with a reciprocating movement by the motion of a ramp transversely to the plunger. The plunger is slightly movably mounted on this ramp. The disadvantage of the design of the slug removal that is described, i.e. the removal of the slug from the hydroforming tool, is that it can be used only for punching nearly vertically downward. Otherwise, the slug cannot follow the backward movement of the plunger in the slug channel of the die button and thus cannot be kicked out of the hydroforming tool by the pusher. This is especially true when a plurality of holes are to be made in the same hollow profile in different circumferential areas. If the pressure is not released until the level of the transverse channel is reached, the slug, which until then is pressed against the end of the plunger by internal high pressure, falls off the plunger back down onto the underside of the cutting edge of the die button.
The goal of the invention is to provide an improved method and device that allows removal of the slug from the hydroforming tool in simple fashion from any position of the slug channel that leads into the die of the hydroforming tool in which the slug is initially received after punching.
This goal is achieved according to the invention by providing a method for removing a slug separated from a hollow profile in an internal high pressure hydroforming tool, said hydroforming tool defining a die cavity and a slug channel communicating with said die cavity, and a plunger movably disposed in said slug channel to be retractable into said slug channel and to be extendable into said die cavity, wherein said slug is separated from the hollow profile by retracting the plunger into the slug channel such that the slug abuts an end of the plunger, said method comprising the acts of: adhering said slug to said end of the plunger; opening said hydroforming tool and removing said hollow profile; extending said end of the plunger with the slug adhered thereto into said die cavity and inserting a removal tool into said die cavity; attracting said slug from said plunger to said removal tool; and removing said removal tool with said slug adhered thereto from said die cavity.
This goal is achieved according to the invention by providing a device for removing a slug separated from a hollow profile by internal high pressure hydroforming, comprising: a hydroforming tool defining a die cavity and a slug channel communicating with said die cavity; a plunger movably disposed in said slug channel to be retractable into said slug channel and to be extendable into said die cavity, said slug being separated from the hollow profile by retracting the plunger into the slug channel such that the slug abuts an end of the plunger, means for adhering said slug to said end of the plunger; a removal tool insertable into said die cavity; and means for attracting said slug from said plunger to said removal tool.
Because of the adhesion means on the plunger, the slug can be held on the plunger at all times without being lost, i.e., both under the influence of internal high pressure and also when the pressure fluid is not under pressure, with the path and the position of the slug channel relative to the die of the hydroforming tool having no significance whatsoever as far as the retention of the slug on the plunger is concerned. When the slug is removed, it is advisable to remove it from the side of the die cavity, open after shaping, of the hydroforming tool with the perforated hollow profile removed. When there are several perforations and thus a plurality of slugs being formed, only a single removal tool is required to receive all the slugs, in contrast to the known method, where several pusher-type removal tools are required. This considerably simplifies the hydroforming tool since no recesses need be provided for the pushers and their drives that would reduce the strength of the hydroforming tool. Because of the adhesive property of the removal tool of the invention, the slug, pushed by the plunger into the die cavity and continuing to adhere to the end of the plunger without falling off, during axial insertion of the removal tool into the die cavity, regardless of which circumferential position the slug is in, comes loose from the plunger and is transferred to the removal tool without being lost, and the tool is then brought out of the hydroforming tool together with the slug. The area of the removal tool with adhesive action can be located on all sides in the circumferential direction, so that the slug can be transferred from the plunger to the removal tool in a simple axial movement. For adaptation to the axial position of the plunger and hence of the slug, a plurality of axially spaced areas can be provided which likewise have adhesive action all the way around in the circumferential direction. The area with the adhesive action can also be concentrated locally on the other side, so that, possibly following axial insertion, the removal tool must be rotated around its own axis in order to be opposite the slug with its adhesion area. In general, the invention makes it simple to automate slug disposal.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.